ESR1 and triple-negative breast carcinoma: Although targeted therapeutics exist for estrogen receptor (ER)-positive (Jordan, 2003) [luminal A/B (Prat and Perou, 2011)] and HER2-positive (Hynes and Lane, 2005) [HER2-enriched (Prat and Perou, 2011)] tumors, targeted treatments for triple-negative breast cancer (TNBC) [basal-like and claudin-low (Prat and Perou, 2011)] remain an important unmet clinical need (Carey et al., 2010).